Superimposition of Carbon Dioxide on Acute Isobaric Hypoxia: Plasma Erythropoietin, Acid-Base Status, and P sub 50 in the Unanesthetized Rabbit

摘要

Major factors affecting changes of the arterial Hb--O sub 2 affinity (P sub 50 ) were examined in relation to the initiation of erythropoietin (ESF) production in unanesthetized New Zealand white male rabbits. They were exposed to an isobaric hypoxic environment (8.8 percent O sub 2 ) with and without CO sub 2 (5.6 percent or 10 percent). During 5 hrs exposure, samples of arterial blood were collected for measurements of plasma ESF titers; whole-blood pH, P/sub CO2/, S/sub O2/, lactate, pyruvate, and P sub 50 ; and intraerythrocytic 2,3-DPG, ATP and ADP. Exposure to 8.8 percent oxygen alone stimulated ESF production and caused a leftward shift in the in vivo P sub 50 ; the addition of CO sub 2 significantly inhibited ESF production and blocked the shift in P sub 50 /sub (i.v.)/. The data suggest that increased oxygenation of the whole-body tissues occurs with exposure to 8.8 percent O sub 2 + CO sub 2 as reflected by lower whole-blood excess lactate accumulation. In keeping with the prevailing theory, the suppression of ESF production is probably a result of this increased oxygenation. (ERA citation 04:001544)